spotting- pregnant or pms?

is it possible to spot about a week before you expect your period to come? 
I'm expecting my period to come in about 5 days but there is a very small chance that I'm pregnant and I just want to know if spotting is only a symptom of being pregnant or if it could've happened as a fluke before getting my period
(unlikely to be pregnant because it was precum from a guy that hadn't 'touched himself' in 2 days)